Neko,
I'll try to get an updated provisioning profile loaded for you this week so you can try the app.
Extension on the headphone cable doesn't really work since the switches on the cable are volume and I'm using the audio system already to speak the call :-) I DO, however now have a little prototype controller (I took video with my iPad at the field the other day, and then promptly left the iPad at the field :-( It's safe though so I'll get it this weekend) that puts a switch where you want it (I put it just above and to the left of the left stick so I can hit it with my finger without taking my hands off the sticks) to advance the call and it worked very nicely!
I've also just finished a little Pebble watch app that can be used (move your wrist/hand) to advance the caller, so if you have a watch you can do that too!

The 0, avg=0 isn't about scoring :-) It's the current force vector the watch is seeing (i.e. the watch was still) and you can choose the threshold movement that will trigger the "next" command.
Now I just need to re-enable voice control for the simulator use case :-)
Thanks everyone for the suggestions! This is too fun! I'll be working on shrinking my prototype down to something easy to secure to your TX. Please let me know if you are interested...
Peter+